Today's Message Index:
----------------------
1. 05:21 AM - WAAS ()
2. 05:42 AM - 91.205 (WAAS) ()
3. 08:12 AM - 91.205 (WAAS) ()
4. 02:02 PM - Re: 91.205 (WAAS) ()
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
1/5/2007
Skip wrote: "I thought the WAAS signal was generated from the ground, am I
wrong?"
Hello Skip, How WAAS works is a bit complex. Here is a brief description
from a US govt web site http://gps.faa.gov/programs/index.htm.
------------------------- BRIEF WAAS DESCRIPTION
BEGINS -----------------------------
"How It Works
Unlike traditional ground-based navigation aids, the WAAS covers nearly all
of the National Airspace System (NAS). The WAAS provides augmentation
information to GPS receivers to enhance the accuracy and reliability of
position estimates.
The signals from GPS satellites are received across the NAS at many
widely-spaced Wide Area Reference Stations (WRS) sites. The WRS locations
are precisely surveyed so that any errors in the received GPS signals can be
detected.
The GPS information collected by the WRS sites is forwarded to the WAAS
Master Station (WMS) via a terrestrial communications network. At the WMS,
the WAAS augmentation messages are generated. These messages contain
information that allows GPS receivers to remove errors in the GPS signal,
allowing for a significant increase in location accuracy and reliability.
The augmentation messages are sent from the WMS to uplink stations to be
transmitted to navigation payloads on Geostationary communications
satellites.
The navigation payloads broadcast the augmentation messages on a GPS-like
signal. The GPS/WAAS receiver processes the WAAS augmentation message as
part of estimating position. The GPS-like signal from the navigation
transponder can also be used by the receiver as an additional source for
calculation of the user's position.
WAAS also provides indications to GPS/WAAS receivers of where the GPS system
is unusable due to system errors or other effects. Further, the WAAS system
was designed to the strictest of safety standards - users are notified
within six seconds of any issuance of hazardously misleading information
that would cause an error in the GPS position estimate."
------------------------------- BRIEF WAAS DESCRIPTION
ENDS --------------------------------
One significant point that I want to make is that while WAAS is not
considered a "ground based system" by the US Govt it still involves "ground
facilities" and 91.205 (d) (2) reads "Two way radio communications system
and navigational equipment appropriate to the ground facilities to be used".
My position is that an ABEA (Amateur Built Experimental Aircraft) equipped
with TSO C146a Gamma-3 certification WAAS avionics complies with 91.205 (d)
(2).
OC -- The best investment we will ever make is in gathering knowledge.
Time: 10:38:28 AM PST US
From: CardinalNSB@aol.com
Subject: Avionics-List: WAAS
I thought the WAAS signal was generated from the ground, am I wrong? Skip
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
1/5/2007
Hello Marcel, Thank you for your input. I welcome information from across
the ocean.
You wrote: "This combined with addition of WAAS may make the difference of
being able to
certify for IFR operation in your experimental."
One of my major points is that there is no such thing as "certifying for IFR
operation" in an ABEA (Amateur Built Experimental Aircraft) here in the US.
The FAA has neither the capability or, under the present FAR's, the process
to certify an ABEA for IFR operations.
Instead, for the equipment required for IFR operations, the builder / pilot
is given the responsibility in the aircraft's Operating Limitations to
comply with FAR 91.205, part of which requires: "Two way radio
communications system and navigational equipment appropriate to the ground
facilities to be used".
OC -- The best investment we will ever make is in gathering knowledge.
Time: 01:52:42 AM PST US
From: "RAS" <deruiteraircraftservices@btinternet.com>
Subject: Re: Avionics-List: Re: 91.205 (WAAS)
Hi,
apologies for butting in on this. We have a RV10 with full Garmin stack and
have had quite some difficulty getting pin outs and ended up sending the
units to an avionics shop to get wired. (we purchased without looms)
I have since spoken to the main Garmin agent in the UK and he explained that
due to complexity of the avionics Garmin does not encourage(read does not
make available pinout)homebuilders to do their own wiring.
This can well be where the snag is in this story. You buy Garmin with a
manufactored loom which is tested for proper function and there's a degree
of assured quality.
This combined with addition of WAAS may make the difference of being able to
certify for IFR operation in your experimental.
It may also be a good idea to print a copy of 91.205 to hand over to your
DAR if he doesn't sign willingly! :-)
Marcel
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
1/5/2007
Hello Bill, Welcome to the world of IFR flight and thanks for your
questions.
You wrote: "....skip....can you explain how one might satisfy the training
and checkride requirements in a WAAS-GPS-only equipped plane with no VHF
nav?"
No, I can't. But let's examine the reality of a WAAS-GPS-only equipped
plane. I can't speak for the high end integrated systems (Chelton, Avidyne,
etc.), but the Garmin 400 / 500 series GPS units that can be upgraded to a
430W or 530W configuration already contain VHF nav capability. I presume the
newly built 430W and 530W boxes will also contain VHF nav capability. So one
will continue to have VHF nav capability even after a WAAS upgrade or new
purchase with these kinds of boxes.
Maybe an issue is whether or not one should plan on / need a separate VHF
nav box such as an SL-30 for back up purposes.**
A) So with an approach qualified GPS (non WAAS capable) and VHF nav one can
have four different instrument approaches to demonstrate to an examiner: 1)
VOR, 2) Localizer, 3) ILS, 4) GPS.
B) With an approach qualified GPS (with WAAS capability) and VHF nav one can
have five different instrument approaches to demonstrate to an examiner: 1)
VOR, 2) Localizer, 3) ILS, 4) GPS, 5) an approach that requires WAAS to
achieve the published minimums.
C) With no approach qualified GPS and only VHF nav one can have three
different instrument approaches to demonstrate to an examiner: 1) VOR, 2)
Localizer, 3) ILS.
And the question of ADF capability in your aircraft doesn't need to raise
its ugly head unless you choose to use some GPS capability to substitute for
a NDB where permitted.
You might want to discuss the above positions with your examiner prior to
showing up for the practical test to determine if he agrees.
OC -- The best investment we will ever make is in gathering knowledge.
**PS: I use my GNS 430 and SL-30 together whenever possible. If one intends
to fly IFR to the extent that an approach capable GPS is needed then I think
the investment in a separate VHF nav box is well justified.
Time: 05:09:11 AM PST US
From: "Bill Boyd" <sportav8r@gmail.com>
Subject: Re: AeroElectric-List: Re: 91.205 (WAAS)
Question from a fledgeling IFR student (meaning I've begun reading for
the written, but have zero instructional time with a live mentor so
far): The practical flight test standards call for 3 different types
of instrument approaches to be made, a requirement that I interpret to
mean an NDB would be required if there were not an approach-certified
GPS on board to substitute for it (localizer and ILS being the other
two types of approach I can think of). Without getting sidetracked
into a discussion of how to avoid unpopular NDB navigation, can you
explain how one might satisfy the training and checkride requirements
in a WAAS-GPS-only equipped plane with no VHF nav? You didn't say
this was the case, but the question has relevance to me as a
homebuilder still planning his IFR panel upgrade.
Thanks, gentlemen.
Bill B.
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: 91.205 (WAAS) |
1/5/2007
Hello Bill,
1) You wrote: " Sorry to cloud any points in the thread."
Not a problem at all -- you gave us an opportunity to broaden the picture a
bit.
2) You wrote: "....skip.....the question more heavily on my mind: about
the adequacy of the WAAS / internal GPS being brought out by Grand
Rapids Tech for the EFIS system I'm planning to install"
Now this raises a very interesting issue. Is GRT going to TSO this
equipment? They haven't gone that route in the past.
Note that paragraph 1-1-20 c of the aim requires that WAAS avionics meet
either TSO C145 or 146A.
Your SL-30 would make it legal to fly IFR, but if your GRT WAAS / internal
GPS in your EFIS is not TSO'd it is not clear to me what additional legal
value it would have when operating IFR. Like any other reasonably capable
GPS unit it could provide very beneficial situational awareness support.
OC -- The best investment we will ever make is in gathering knowledge.
----- Original Message -----
From: "Bill Boyd" <sportav8r@gmail.com>
Sent: Friday, January 05, 2007 1:33 PM
Subject: Re: 91.205 (WAAS)
> OC, let me fess up here... I forgot that the GNS-430 includes the vhf
> nav comm side of things! I read the actual words in your post, but my
> brain fast-forwarded to the question more heavily on my mind: about
> the adequacy of the WAAS / internal GPS being brought out by Grand
> Rapids Tech for the EFIS system I'm planning to install, the one that
> would let me omit the 430 from my purchase list and use just an SL30
> in its place (and save mega-thousands). So my question was based in
> part on faulty assumptions of what was inside the 430-<head slap!> and
> partly on my impatience to get my own questions answered. Sorry to
> cloud any points in the thread.
>
> -Bill B.
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|